Production of cyclohexane from naphtha



Oct. 15, 1968 1, W, DAWSQN ETAL 3,406,217

PRODUCTION 0F CYCLOHEXANE FROM NAPHTHA Filed March 5l, 1966 4 7N [RAFFINATE v sToN u (jr rom/25 United States Patent O 3,406,217 PRODUCTION OF CYCLOHEXANE FROM NAPHTHA Joseph W. Davison, John F. Hutto, and Richard J.

Livingston, Bartlesville, Okla., assignors to Phillips Petroleum Company, a corporation of Delaware Filed Mar. 31, 1966, Ser. No. 539,083 7 Claims. (Cl. 260-666) ABSTRACT OF THE DISCLOSURE A process of producing cyclohexane from a petroleum naphtha stream wherein the naphtha stream is fractionated ina distillation zone to form an overhead fraction containing Cs and lighter, an intermediate fraction containing benzene, methylcyclopentane, and cyclohexane, and a bottom fraction containing Cqs and heavier. The bottom fraction is passed to a cracking zone wherein a benzenecontaining stream is formed which is then combined with the intermediate fraction from the distillation zone. The resulting combined stream is then passed through an extraction zone wherein parainic hydrocarbons are removed therefrom. The effluent from the extraction zone is passed through a benzene hydrogenation zone wherein benzene is hydrogenated to cyclohexane, and the eiuent from the benzene hydrogenation zone is passed through an isomerization zone wherein methylcyclopentane is converted to cyclohexane. A pure cyclohexane stream is removed from the isomerization zone.

This invention relates to the production of cyclohexane from naphtha. In one of its aspects, it relates to a process for the production of cyclohexane from a naphtha containing steam, the process comprising fractionating the naphtha stream to recover an overhead portion, a bottoms portion, and an intermediate stream containing hydrocarbons boiling in the benzene range; cracking the bottoms portion from the fractionator to produce an olefin-containing stream, a stream boiling in the gasoline range, and a benzene boiling range stream; combining the benzene boiling range stream with the intermediate stream from the fractionator, from which combined stream can be obtained a high quality cyclohexane product. In another of its aspects, the invention relates to a process for producing cyclohexane from naphtha as hereinbefore described wherein the combined stream of benzene-forming hydrocarbons is passed to a solvent extraction zone for removal of parains, and the remaining benzene boiling range stream is hydrogenated to produce cyclohexane from benzene and a resulting stream is isomerized to produce cyclohexane from methylcyclopentane. In another of its aspects, the invention relates to a process for the production of cyclohexane from naphtha as hereinbefore described wherein the overhead portion from the fractionator and the parain containing raflinate phase from the solvent extraction step are combined with the bottoms from the fractionator prior to the cracking step. In a still further aspect, the invention relates to an apparatus for carrying out the aforementioned processes.

Naphtha, which is readily obtained from certain crude oils, is cracked to produce oleins and diolefns in the C2 to C5 range and paraflins boiling in the gasoline range. It is known that the naphtha also contains a small fraction of benzene and other hydrocarbons boiling in the benzene range. However, heretofore it has been uneconomical to recover these hydrocarbons from naphtha. With increasing quantities of naphtha being cracked, and with increasing demand for cyclohexane which is used as an intermediate in the production of nylon, it has now been found economically feasible to recover a benzene fraction from crude naphtha.

3,406,217 Patented Oct. 15, 1968 We have now discovered that cyclohexane can be produced from a naphtha fraction by removing the heart cut of naphtha prior to cracking, combining a cracked naphtha product fraction containing benzene and cyclohexane with the heart cut from the naphtha fraction and treating the products to produce a high quality cyclohexane.

By various aspects of this invention, one or more of the following, or other, objects can be obtained.

It is an object of this invention to provide a process and apparatus for the maximum recovery of cyclohexane from crude naphtha fraction.

It is a still further object of this invention to provide a process and apparatus for the maximum production of cyclohexane wherein olens and diolens are simultaneously produced with increased efficiency.

Other aspects, objects, and the several advantages of this invention are apparent to one skilled in the art from a study of this disclosure, the drawing and the appended claims.

According to the invention, cyclohexane is recovered as a product of the process from a naphtha containing stream. The naphtha containing stream is fractionated and the heart cut containing hydrocarbons boiling in the benzene range are removed. The heart cut from the fractionator is treated in a solvent extraction zone to remove parains therefrom, and is passed to a benzene hydrogenator to produce cyclohexane from benzene and then to an isomerization step wherein methylcyclopentane is converted to cyclohexane.

According to one embodiment of the invention, the heavy product from the fractionator is cracked to produce an olen and diolen containing stream, a benzene containing stream, and a gasoline boiling range stream. The benzene containing stream can be admixed with the heart cut from the fractionator. In another embodiment of the invention, the overhead from the fractionator and the rathnate from the solvent extraction zone are combined and admixed with the bottoms from the fractionator prior to the cracking step.

The invention will now be described with reference to the accompanying drawing which shows an embodiment of the invention.

A naphtha stream passes through line 1 into fractionator 2 which separates the naphtha into a heavy bottom fraction which is yremoved through line 4, an overhead fraction containing C5 and lighter hydrocarbons, and a heart cut containing hydrocarbons boiling in the benzene boiling range. The overhead fraction is removed through line 3 and the 'benzene boiling range fraction is removed through line 5 and passed to a solvent extraction zone 6- wherein a solvent such as methylcarbitol is used as a solvent. Suitable conditions in fractionator 2 are a top temperature of 210 to 250 F., a bottom temperature of 250 to 300 F., and a pressure of 55 to 65 p.s.i.a. The paraincontaining raffinate from the solvent extraction zone 6 is removed through line 7 Iand combined with the over-head from fractionator 2 in line 3. The combined streams are further combined with the bottoms from fractionator 2 in line 4 and passed to cracking zone 8. Cracking zone `8- can be any conventional cracking reactor such as a catalytic cracker or thermal cracker. The eflluent from the cracking reactor 8 passes through line 9 and is quenched in 23 to remove heavy ends. The etlluent from 23 is passed to fractionator 10 wherein olens and diolens are removed through line 11 and heavier `boiling hydrocarbons are passed through line 12 to fractionator 13 wherein gasoline boiling range hydrocarbons and heavier hydrocarbons are removed through line 15 and a benzene containing fr action is removed through line 14. Suitable operating conditions for the fractionator 10 yare a top temperature of 25 to 50 F., bottom temperature of 200 to 250 F., and Reasonable variation and modication are possible with- 100 t 150 p.s.i.a. Suitable operating conditions for fracin the scope of the foregoing disclosure, the drawing and tionator 13 are a top temperature of 150 to 200 F., botthe appended claims to the invention, the essence of which tom temperature of 250 to 400 F., and` a pressure of 50 is that there has been provided a process and apparatus to 75 p.s.i.a. The benzene containing stream in line 14 5 for the production of cyclohexane from a naphtha fraction is passed to a mild hydrogenation zone 16 wherein unby removing the heart cut from the naphtha fraction, resaturated compounds such as olelins, dioleins and acetymoving the parainic material from the heart cut, cracking lenes are converted to saturated compounds. The efiiuent the remaining naphtha fraction to produce olens and from hydrogenation zone 16 is passed through line 17 and gasoline boiling range hydrocarbons, and a benzene boilcombined with the benzene boiling range stream in line 5. ing range hydrocarbon fraction, and combining the ben- The euent from the solvent extraction zone 6 is passed zene boiling range hydrocarbons 'with the heart cut of the through line 18 to hydrogenation zone 19t wherein benzene naphtha.

is converted to cyclohexane. In hydrogenation zone 19, We claim:

benzene is contacted with hydrogen in the presence of a 1. A process for producing cyclohexane from a petrohydrogenation catalyst such as nickel at a temperature in leurn naphtha fraction containing benzene, methylcyclothe range of 350 F. to 500 F. A benzene free hydropentane, cyclohexane, and paraflnic hydrocarbons concarbon euent is withdrawn from hydrogenation zone 19 taining from 1 to at least 8 carbon atoms comprising: via conduit 20 and passed to liquid isomerization zone 21 (a) passing said naphtha fraction to a distillation zone; wherein methylcyclopentane within the feed mixture is (b) removing an intermediate fraction containing ben- SOmeIiZed t0 cyclohexane Contacting th feed a 20 zene, methylcyclopentane, and cyclohexane an over.. conventional isomerization catalyst such as HC1 promoted head fraction Containing Pentanes and lighter parafaluminum halide fIOmPleX-ype Catalyst- When employing iinic hydrocarbons, and a bottom fraction containing au aluminum hahde Complex-type Catalyst, the temPeTa' heptanes and heavier paratlinic hydrocarbons from ture and pressure of the isomerization zone is preferably maintained typically in the range of 100 F. to 160 F. 25 and in the range of 100 to 250 p.s.i.a., respectively. The isomerization zone eluent is removed through line 22 and the cyclohexane is removed from the impurities by conventional means, not shown.

Thus, according to the invention, cyclohexane is eiciently produced from a naphtha fraction. Further, bestream lth Saldmtermedl'flte frac'tlon cause the benzene boiling fraction has been removed from (e) removmg paraffin Constltuents from the Combufed the naphtha, a greater percentage of parains are passed Stream of Step (d) to form a benzene'hydrogenauon to the cracking zone. This yields an improved amount of u feed st ream; olefins from the cracking zone. Thus, the process, while 3* (f) PaSSlng Sald benzene-hydrogenation feed stream said distillation zone;

(c) passing said bottom fraction to a cracking zone wherein at least a portion thereof is transformed to benzene, olens, and diolens;

(d) separating a benzene-containing stream from said cracking zone and combining said benzene-containing producing cyclohexane, also increases the yield of olefins thfllgh a benzene-hydrogenation zone wherein benfrom the naphtha fraction zene 1s converted to cyclohexane;

As a specific example of how this invention works, the (g) PaSSlng the effluent ff'om 1h? @Bleue-hydrogen?" following table giving a material balance for the opera- 40 UOII 2011 through an ISOmeIIZalOH Zone Whefell tion as described in the drawing is shown. The units given methylcyclopentane 1s converted .to cyclohexane; and are pounds per hour. (h) removing cyclohexane from said isomerization zone.

TABLE Stream number 1 3 4 5 7 9 11 Prefractlonator OHD BTMS Side-Draw Paratlin Cracking Oletn feed Recycle efuent product n 214 1, 429 1, 429 Ethane and ghter 2 4 454 10B 24 24 64 25s 250 194 13 11 214 21 a 38e 14 Met hylcyclupentane 324 11 Benzene 96 206 Cyclohexane. 252 9 Heptanes 624 172 Oetanes 558 131 Heavier 546 270 Total, 1b./hr 2, 582 3, 010

Stream number 2nd Fract. Hydro-treater Heavy Hydro eluent Extract Hydrogenation Cyclohexane feed feed product (recycle) efliuent concentrate Ethane and lighter Hexanes Benzene Heuvier 270 270 Total, 1b.]h1 798 290 508 290 860 884 884 2. The process of claim 1 wherein said parafnic constituents are removed in step (e) by solvent extraction.

3. A process according to claim 1 wherein said overhead from said distillation zone is combined with said bottoms prior to said cracking step.

4. A process according to claim 2 wherein parafnic rainate from said solvent extraction zone is combined with said bottoms from said distillation zone prior to said cracking step.

S. A process according to claim 2 wherein said overhead from said distillation zone and said paratinic raffinate from said solvent extraction zone are combined with said bottoms from said distillation zone prior to said cracking step.

6. The process of claim 1 wherein step (d) comprises quenching the efuent from said cracking zone; passing the quenched efuent to a second distillation zone wherein olens and diolefins are removed as overhead and a heavier fraction containing benzene is removed from the bottom thereof; passing said heavier fraction .to a third distillation zone wherein a benzene-boiling range fraction containing benzene, olens, and dioletins is removed as overhead and a stream containing heptanes and heavier hydrocarbons is removed from the bottom thereof; passing said benzene boiling range fraction through a mild hydrogenation zone wherein olens and diolefins contained ltherein are converted to saturated compounds; removing said benzenecontaining stream from said mild hydrogenation zone.

7. A process according to claim 2 wherein said solvent is methylcarbitol.

References Cited UNITED STATES PATENTS 2,415,066 1/1947 Ross et al 260-666 2,505,792 5/1950 Ross et al. 260-666 2,809,222 10/ 1957 Hawkins et a1 260-666 2,831,038 4/1958 Morrison et al. 260-666 3,211,797 10/1965 Houston 260-666 DELBERT E. GANTZ, Primary Examiner.

V. OKEEFE, Assistant Examiner. 

